This invention relates generally to process and plating systems, and in particular, to an automatic multi-wafer process system that is characterized by horizontal transport of vertically-oriented wafers through one or more process cells and processing of vertically-oriented wafers within one or more process cells.
Prior art automatic multi-wafer plating systems typically perform the plating of wafers in a horizontal manner. That is, the plating of a wafer occurs in a process where the wafer is oriented horizontally. In the typical case, a wafer is oriented horizontally with the plating surface facing downwards. Then, plating solution is directed upwards towards the plating surface of the wafer to form the plating deposition. In another case, a wafer is oriented horizontally with the plating surface facing upwards. Then, the wafer is immersed in a plating solution bath and fresh plating solution is directed down towards the plating surface of the wafer to form the plating deposition. In either case, if the plating process is electrolytic, a voltage potential is applied across the plating solution by an anode electrode exposed to the plating solution and a cathode electrode in contact with the plating surface of the wafer.
The automatic processing of multiple wafers using the horizontal processing of prior art plating systems typically involve a centralized robotic wafer loader surrounded by several process cells. This type of arrangement is referred to in the relevant art as a xe2x80x9ccluster toolxe2x80x9d. In a cluster tool, a process cell may have more than one head in order to process multiple wafers simultaneously. In operation, the centralized robotic wafer loader loads a first set of wafers into a first process cells (e.g. cleaning and activation). When the first process is complete, the centralized robotic wafer loader transfers the first set of wafers angularly to the second process cell (e.g. electroplating) and then loads a second set of wafers into the first process cell. The centralized robotic wafer loader keeps loading and transferring wafers from process cell to process cell until the wafers have undergone all of the specified processes.
A drawback of the cluster tool arrangement stems from the fact that the centralized robotic wafer loader inserts and removes wafers from process cells many times during a run. Thus, the wafers are more susceptible to contamination and defects due to frequent handling by the centralized robotic wafer loader. Another drawback of the cluster tool arrangement stems from the fact that the process cells are arranged around the centralized robotic wafer loader. Often, there is a need to service the plating system as well as expel gases and/or liquids from process cells to maintain the integrity of the clean room environment. This is typically done through the rear of the process cells into a chase room by way of a clean room wall. Accordingly, in a cluster tool arrangement, it is more difficult to arrange the clean room wall and chase room to accommodate the circular arrangement of the process cells.
Thus, there is a need for a wafer processing system that can process wafers through one or more process cells without the need of frequently loading and unloading wafers into and from process cells. There is also a need for a wafer processing system that can interface relatively easy with a chase room for servicing and expulsion of unwanted gas and liquids. Such needs and others are met with the wafer processing system and related methods in accordance with the invention.